我有2类Item和LineQuote。 通过填写行引号表格，当我选择一个项目时，我希望自动填写指定字段和单位字段。

class Item(models.Model):
    code = models.CharField(max_length=20,blank=False)
    designation = models.CharField(max_length=200,blank=False)
    unit = models.CharField(max_length=10,choices=choices_unite,default='')

    class Meta:
        ordering =('code',)


    def __str__(self):
        return self.code


class LineQuote(models.Model):
    num_quote= models.ForeignKey('Devis',null= True,on_delete=models.CASCADE)
    article = models.ForeignKey('Article',on_delete=models.CASCADE)
    designation = models.CharField(max_length=200,default='')
    quantity = models.IntegerField(blank=True,null=True)
    discount = models.IntegerField(blank=True,null=True,default=0)
    price = models.FloatField(blank=True,null=True)